The Taliban have claimed responsibility for an attack in which at least 19 people died at a university in Pakistan.

Four of the attackers are known to have been killed at the campus building in Khyber Pakhtunkhwa province, in the country's northwest.

Militants used the cover of thick, wintry fog to scale the walls of the Bacha Khan University in the town of Charsadda, about 18 miles (30km) from the city of Peshawar.

They then went into university buildings and began to open fire on teachers and students in classrooms. 

Explosions were heard inside and TV pictures showed heavily armed security personnel heading into the compounds as female students ran for their lives.

At the university gates, distraught relatives of those being taught inside anxiously waited for news.

Regional police chief Saeed Wazir said most of the student victims shot dead at a hostel for boys on the campus site.

"More than 30 others including students, staff and security guards were wounded," he added, but another official said the number killed could rise to as high as 40.

It is not known if the 19 included the four dead attackers, but at least one lecturer is among those who lost their lives.

Witnesses said the teacher, chemistry professor Dr Hamid, attempted to shoot back at the militants.

Geology student Zahoor Ahmed said: "He was holding a pistol in his hand.

"Then I saw a bullet hit him. I saw two militants were firing. I ran inside and then managed to flee by jumping over the back wall."

Another told TV reporters: "We saw three terrorists shouting, 'Allah is great!' and rushing towards the stairs of our department.

"One student jumped out of the classroom through the window. We never saw him get up."

"We saw (the chemistry professor) fall down and as the terrorists entered the (registrar's) office we ran away."

The university teaches over 3,000 students and was hosting an extra 600 visitors on Wednesday for a poetry recital, according to its vice chancellor Fazal Rahim.

Umar Mansoor, a commander in the Tehreek-e-Taliban Pakistani (TTP) militant group told AFP: "Our four suicide attackers carried out the attack on Bacha Khan University today."

He added that the attack it was in retaliation for a military offensive against extremists in tribal areas.

The attack comes a little over a year after Taliban gunmen killed 134 students at a military-run school in nearby Peshawar.

(Sky News)